If you use Wordpress, and want to see the keyword density of your own posts, use Yoast plugin, it's really good.

Keyword density checker

tools.seobook.com/general/keyword-density/

Search on Google, you will get plenty of results...

Many free keyword density checker tool but http://www.live-keyword-analysis.com/ is best.

Just Google it yourself and there will you found lots of results about your query.

smallseotools and majesticseo is also better optionwith woorank.

There are many online tools available. Just Google it out and check the results.

you can also try word counter online that checks the number of words along with the keywords .